Listing 1. trillian.fw

#!/bin/sh 
#
#  Firewall Builder  fwb_ipt v1.0.8-3 
#
#  Generated Tue Mar 11 08:01:21 2003 CST

log() {
  if test -x "$LOGGER"; then
    logger -p info "$1"
  fi
}

MODPROBE="/sbin/modprobe"
IPTABLES="/sbin/iptables"
IP="/sbin/ip"
LOGGER="/usr/bin/logger"

cd /etc || exit 1

log "Activating firewall script..."

va_num=1

FWD=`cat /proc/sys/net/ipv4/ip_forward`
echo "0" > /proc/sys/net/ipv4/ip_forward
echo 30 > /proc/sys/net/ipv4/tcp_fin_timeout
echo 1800 > /proc/sys/net/ipv4/tcp_keepalive_intvl

$IP -4 neigh flush dev eth0
$IP -4 addr flush dev eth0 label "eth0:FWB*"

$IPTABLES -P OUTPUT  DROP
$IPTABLES -P INPUT   DROP
$IPTABLES -P FORWARD DROP

cat /proc/net/ip_tables_names | while read table; do
  $IPTABLES -t $table -L -n | \
  while read c chain rest; do
      if test "X$c" = "XChain" ; then
        $IPTABLES -t $table -F $chain
      fi
  done
  $IPTABLES -t $table -X
done

$IPTABLES -A INPUT   -m state \
--state ESTABLISHED,RELATED -j ACCEPT
$IPTABLES -A OUTPUT  -m state \
--state ESTABLISHED,RELATED -j ACCEPT
$IPTABLES -A FORWARD -m state \
--state ESTABLISHED,RELATED -j ACCEPT

# Rule 0(lo):  Outbound from loopback
$IPTABLES -A OUTPUT  -o lo -j ACCEPT 

# Rule 1(lo): Inbound from loopback
$IPTABLES -A INPUT  -i lo -j ACCEPT 

# Rule 0(global)
$IPTABLES -A INPUT -p tcp  -m multiport  \
--destination-port 80,443  -m state \
--state NEW -j ACCEPT 

# Rule 1(global)
$IPTABLES -A OUTPUT -p tcp  --destination-port 53 \
-m state --state NEW -j ACCEPT 
$IPTABLES -A OUTPUT -p udp  --destination-port 53 \
-m state --state NEW -j ACCEPT 

# Rule 2(global)
$IPTABLES -A INPUT -p tcp  -s 192.168.111.0/24  \
--destination-port 22  -m state --state NEW \
-j ACCEPT 

# Rule 3(global)
$IPTABLES -N RULE_3
$IPTABLES -A FORWARD -j RULE_3 
$IPTABLES -A RULE_3 -j LOG  --log-level warning \
--log-prefix "RULE 3 -- DROP "  --log-ip-options 
$IPTABLES -A RULE_3 -j DROP 

echo 0 > /proc/sys/net/ipv4/ip_forward